Vol. 31, pp. 21-26 May 16, 1918 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



FIVE NEW MAMMALS FROM ARIZONA AND COLORADO. 



BY E. A. GOLDMAN. 



Study of recent collections of mammals from various western 

 States reveals the existence of five hitherto unrecognized geo- 

 graphic races. At least two of these present color characters 

 which indicate strong reaction to environmental conditions. 



The new forms are characterized as follows: 



Sigmodon hispidus confinis, subsp. nov. 



GILA COTTON RAT. 



Type from Safford, Arizona (altitude 2,900 feet). No. 204241, cT adult 

 (molars rather slightly worn), U. S. National Museum (Biological Survey 

 Collection), collected by J. L. Peters, July 27, 1914. Original number 77. 



Geographic distribution. — Upper part of the Gila River Valley in south- 

 eastern Arizona. 



General characters. — A rather small subspecies similar in general to 

 Sigmodon hispidus berlandieri, Sigmodon h. arizonae, and Sigmodon h. ere- 

 micus, but darker than any of these forms, with skull narrower, less 

 massive and differing in important details. 



Color. — Upperparts near pinkish-buff (Ridgway, 1912) heavily mixed 

 or lined with blackish over top of head and back, the latter element 

 thinning out along cheeks, shoulders and sides ; underparts and feet dull 

 whitish or grayish; ears usually grayish, but varying to buffy inside; tail 

 brownish above, grayish below. 



Skull. — Similar to those of S. h. berlandieri, S. h. arizonae, and S. h. ere- 

 micus, but narrower and less massive than any of them ; rostrum narrower ; 

 much smaller than that of S. h. arizonae, with frontals less acutely pro- 

 longed posteriorly, and interparietal and audital bullae relatively smaller; 

 interparietal and audital bullae small, much as in S. h. eremicus, but 

 dentition lighter. 



Measurements.— Type; Total length, 277; tail vertebrae, 111; hind foot, 

 31. Skull: Greatest length, 34.3; zygomatic breadth, 19.2; interorbital 

 breadth, 4.8; nasals, 13.2; width of braincase (in front of descending 

 process of supraoccipital), 13.2; maxillary toothrow, 6. 



6— Proc. Biol. Soc. Wash.. Vol. 31. 1918. (21) 



